The chief executive of BHP Billiton, Marius Kloppers, is set to retire and will be succeeded by Andrew Mackenzie, the mining firm's base metals chief.

Mr Kloppers will retire as chief executive and director on May 10, and will leave the group on October 1.

The Board has decided that Andrew is the right person to lead BHP Billiton in a changing global environment

The announcement came as BHP Billiton reported today that its profits were down to $US5.7 billion in the first half of 2012-13, a fall of 43 per cent on a year earlier due to lower commodity prices and the high dollar.

"Marius was appointed chief executive just prior to the global financial crisis. Despite an exceptionally difficult economic environment during his tenure, Marius and his team have delivered for shareholders, significantly outperforming our peers in terms of total shareholder returns," Mr Nasser said.

"He drove new investments into next generation opportunities including US onshore gas and liquids and created one of the most valuable companies in the world."

Mr Nasser said the change was a result of the company's succession planning process.

"The Board has decided that Andrew is the right person to lead BHP Billiton in a changing global environment," he said, adding that the move and Mackenzie's background should not be seen as shift in the firm's strategy or emphasis.

"He's a rare executive because he has experience in both the oil and gas, petrochemicals and minerals area of this business. And that fits us perfectly."

Mr Mackenzie, who oversees much of the company's portfolio, including key copper mines at Escondida in Chile, said it would be a privilege to lead BHP Billiton.

A prize-winning scientist who grew up in an industrial town near Glasgow, Mr Mackenzie spent 22 years at BP and three at Rio before becoming the head of BHP's non-ferrous division in November 2008.

He speaks five languages, including French, German and Spanish, and has lived in six countries on four continents.

"I look forward to working closely with Marius during the transition and building on his legacy," he said, adding in a press conference this morning that "there is no other job I'd rather do".

Mr Mackenzie will move to Melbourne with his wife.

The 'right appointment'

Paul Young of Deutsche Bank said Mr Mackenzie was the ''right appointment'' for BHP and had a depth of experience in onshore and offshore petroleum, and in base metals.

''So therefore if the incremental dollar for the company beyond iron ore and [metallurgical] coal is going into petroleum and the non-ferrous division, then he is the right appointment to deliver on the growth beyond that,'' Mr Young said.

"He has great understanding of the US onshore business and of the more difficult technical assets in the portfolio - growth assets such as Olympic Dam and Jansen."

Hayden Bairstow of CLSA Asia-Pacific Markets said the announcement was not a surprise, and that Mr Mackenzie was seen as the man most likely to take over the role.

''There was some potential they may have looked externally, but that wasn't high,'' Mr Bairstow said.

''I think he was the best man for the job internally. He's familiar with the business having been there for a while.

"The reality is commodity prices are no longer rising, so he needs to be much more focused on removing costs out of the business and making more conservative growth decisions, which in his role ... as the head of the copper business has had its own cost issues in the past."

Mark Taylor, a senior resources analyst at Morningstar, said the market would welcome Mackenzie's expertise in energy.

"The new CEO is coming from a very long career in oil and gas and minerals, especially oil and gas. And oil and gas is a growing proportion of BHP's business. So I think it will be well received by the market," he said.

Time to move on

Mr Kloppers said it was a difficult decision and that "deciding the right time to retire was never going to be easy". But he added that he believed it was the right time to move on.

BHP said details of Mr Mackenzie's remuneration would be released before he becomes chief executive, while Mr Kloppers' leaving arrangement will be announced on May 10.

Last year BHP shelved $US40 billion in projects and shut some loss-making coal mines, as the industry battled with soaring costs, a strong Australian dollar and sliding commodity prices.

The company's succession planning process was the subject of speculation at the firm's annual meeting in November, with Mr Mackenzie and Alberto Calderon among those touted as possible candidates for the chief executive's role.

But BHP refused to put a timeline on the process.

The announcement to the market this morning came just a month after Tom Albanese stepped down from mining giant Rio Tinto and was replaced by Sam Walsh as chief executive.

Mr Nasser said Mr Albanese's departure was "interesting to note" but did not influence the decision-making process at BHP.